Jaeger-LeCoultre Duometre Chronograph Moon

In 2007, Jaeger-LeCoultre introduced the revolutionary Duometre mechanism with a chronograph version, a pinnacle of precise timekeeping. Fast forward to 2024, the Maison has innovatively integrated the Duometre concept into a new model that merges the meticulous accuracy of a chronograph with the alluring complexity of a celestial complication. This new piece, driven by the Calibre 391, is called the Duometre Chronograph Moon. It combines the quick functionality of a chronograph, capable of measuring time intervals down to 1/6th of a second, with the gradual progression of the moon phase, which completes a cycle every 29.53 days, alongside a Night and Day indicator.

At Watches and Wonders 2024, Jaeger-LeCoultre unveiled two versions of the Duometre Chronograph Moon: one encased in platinum with a copper-colored dial and another in pink gold with a silver dial. Each model is complemented by a hand-stitched alligator strap, lined with smaller scale alligator leather, enhancing their sophisticated aesthetics.

The introduction of the Duometre mechanism in 2007, which features two separate barrels and gear trains within a single caliber linked to a single escapement, marked a significant innovation. This design ensures that the operation of the complications does not interfere with the escapement’s function, preserving the movement’s isochronism. This groundbreaking concept was inspired by a historical precursor from the Manufacture—the LeCoultre Calibre 19/20RMSMI of 1881, which also featured dual barrels but did not separate the gear trains, thus not fully resolving the interference issue.

The challenges of incorporating complex functions like the chronograph, which demands short bursts of high power, were what initially drove Jaeger-LeCoultre to develop the Duometre. The mechanism has since been adapted to include other complications such as moon phases, travel time, and a tourbillon.

The newly developed Calibre 391 starts from scratch, featuring a manually wound mono-pusher chronograph integrated with a moon phase and a day-night indicator, plus dual power reserve indicators and a seconde foudroyante (flying second) display. The latter dazzles by completing a full rotation every second, subdividing into six beats, and providing extraordinarily precise readings when the chronograph is stopped.

The design of the Duometre Chronograph Moon includes open-worked sections on the dial that provide a view into the intricate workings of the mechanism, matched by an equally detailed view through the transparent case-back. Here, the movement displays an elaborate construction of floating bridges and open-worked components, all meticulously finished with sunrayed Geneva stripes—a challenging and precise decoration technique that aligns perfectly from the centre to the edges of the calibre once assembled.

Furthermore, the dial design is intuitive yet sophisticated, featuring a traditional three-counter layout with finely textured opaline finishes contrasted by azuré decorated rings. The integration of the moon phase within the chronograph sub-dial at 3 o’clock and the Night and Day display within the time sub-dial at 9 o’clock enhances both functionality and aesthetic balance. The watch also features a seconde foudroyante at 6 o’clock, flanked by two power reserve displays, each indicating 50 hours for its respective barrel—one wound forwards for timekeeping, and one wound backwards for the complications.

For 2024, Jaeger-LeCoultre also introduced a new case design for the Duometre series, echoing the Maison’s 19th-century savonette pocket watches. This new case combines modern aesthetics with tactile appeal, featuring a convex crystal and a smoothly rounded bezel. Measuring 42.5 mm in diameter, the case comprises 34 parts with the lugs attached via screws, allowing for a variety of finishes that play with light as the watch moves.